ci: fix tilde expansion in coder ssh commands, for #71

Replace ~/drupal-core with /home/coder/drupal-core — tilde does not
expand when passed as a literal argument through coder ssh.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: rfay

.github/workflows/drupal-integration-test.yml

@@ -126,7 +126,7 @@ jobs:
 
       - &verify-webroot
         name: Verify workspace — web root exists
-        run: coder ssh ${{ env.WORKSPACE_NAME }} -- test -f ~/drupal-core/web/index.php
+        run: coder ssh ${{ env.WORKSPACE_NAME }} -- test -f /home/coder/drupal-core/web/index.php
 
       - &verify-drush
         name: Verify workspace — Drush DB connected
@@ -271,11 +271,11 @@ jobs:
         run: coder ssh ${{ env.WORKSPACE_NAME }} -- ddev --version
 
       - name: Verify workspace — web root exists
-        run: coder ssh ${{ env.WORKSPACE_NAME }} -- test -f ~/drupal-core/web/index.php
+        run: coder ssh ${{ env.WORKSPACE_NAME }} -- test -f /home/coder/drupal-core/web/index.php
 
       - name: Verify workspace — issue branch checked out
         run: |
-          CURRENT=$(coder ssh ${{ env.WORKSPACE_NAME }} -- git -C ~/drupal-core/repos/drupal branch --show-current)
+          CURRENT=$(coder ssh ${{ env.WORKSPACE_NAME }} -- git -C /home/coder/drupal-core/repos/drupal branch --show-current)
           echo "Current branch: $CURRENT  Expected: ${{ env.ISSUE_BRANCH }}"
           [[ "$CURRENT" == "${{ env.ISSUE_BRANCH }}" ]] || { echo "ERROR: wrong branch" >&2; exit 1; }